In the state of the art, the product 1,3-butadiene is prevalently provided by Steam Cracking processes from which it is selectively extracted from streams containing C4 products or by the dehydrogenation of C4 olefins and C4 paraffins. With respect to the dehydrogenation, the technologies in use are the “Catadiene” process of CB&I Lummus technology, and the “OXO-D Process” developed by Petro-Tex (currently Texas Petrochemicals). Both of these processes are described in Perp Report Nexant Chem Systems Butadiene/Butylenes 09/10-5.
The “Catadiene” technology operates on a fixed adiabatic bed and under vacuum. As the catalyst must be frequently regenerated (the cycles last for less than an hour), more reactors are necessary for production continuity. The catalyst used is an extruded product based on chromium oxide and alumina.
The critical aspects linked to the Catadiene technology are described hereunder. The residual hexavalent Chromium, which therefore remains on the catalyst, is toxic and consequently has a significant environmental impact. The reaction takes place in the same reactor in which the catalyst is regenerated by air, thus creating conditions for a potential risk due to the mixing of air with hydrocarbon, in the case of a breakdown in the programming sequence of the large motorized valves for intercepting the streams between dehydrogenation, stripping, regeneration, stripping.
The ovens in which the feedstock is preheated, before being introduced into the catalytic bed, are sources of gaseous pollutants in particular NOx. As reactors for regeneration and stripping are required in addition to the reaction, the reaction volumes are high with significant investments.
The “OXO-D” technology operates with a fixed bed reactor in which the oxidative dehydrogenation of butenes is carried out, which are fed to the reactor mixed with vapour and air. This process operates without regeneration of the catalyst. There are essentially two critical aspects of the “OXO-D” technology.
The presence of oxygen imposes a severe section for the purification of 1,3-butadiene from oxygen, the latter being critical for the polymerization of 1,3-butadiene. The selectivity to useful product suffers from the presence of oxygen which favours the formation of combustion products consequently requiring that the OXO-D process operates through campaigns when there is a significant difference in price of 1,3-butadiene and that of butenes.
Various patents and patent applications are known, which describe catalytic compositions based on gallium, tin, platinum and alkaline or alkaline earth metals that the Applicant has listed hereunder:
US 2010168493 discloses:                a multi-metallic catalyst based on noble metals for dehydrogenation reactions starting from hydrocarbons, preferably light paraffins such as butanes and iso-butanes, or pentanes and iso-pentanes.        the use of the catalyst described in a dehydrogenation process of light paraffins (C4-C5) recovered after the extraction of unsaturated compounds from fractions coming from steam-cracking or catalytic-cracking.        
The multi-metallic catalyst described in US 2010168493 comprises a noble metal M selected from Pt, Pd, Rh, Ir, at least one promoter X1 selected from Sn, Ge, Pb, possibly at least one promoter X2 selected from Ga, Ir and Tl, an alkaline or alkaline earth metal, supported on a substrate selected from Mg oxides, Ti oxides, Zr oxides, alumina, silica and mixtures thereof (silico-aluminates), wherein the atomic ratio X1/M ranges from 0.3 to 8, wherein the ratio Hir/M is higher than 0.4 and the bimetallic index BMI is higher than 108. The quantity of noble metal ranges from 0.01% wt. to 10% wt.
US 2005033101 discloses:                a catalytic composition containing a noble metal, an alkaline or alkaline earth metal, a compound selected from Sn, Ge, Pb, In, Ga, Tl or mixtures thereof;        a catalytic composition containing a noble metal (Pt), an alkaline or alkaline earth metal present as both metal and oxide, a third component selected from Sn as both metal and oxide, Ge, Pb, In, Ga, Tl and mixtures thereof, supported on a carrier having a surface area lower than 120 m2/g combined with a bulk apparent density higher than 0.5 g/cm3;        a process comprising a catalytic dehydrogenation step in a fluid or mobile bed starting from hydrocarbons such as paraffins and C2-C30 olefins, in particular butanes, which generates a stream rich in hydrogen in vapour phase, a separation step which generates a liquid stream rich in hydrocarbons which is further separated according to a fractionation scheme.        
According to US 2005033101, the carrier of the catalyst is alumina and it is essential for it to have a surface area lower than 120 m2/g combined with a bulk apparent density higher than 0.5 g/cm3. It is also essential for the molar ratio of the alkaline or alkaline earth metal on the third component to be higher than 16. Finally, the quantity of Pt ranges from 0.01% wt. to 5% wt with respect to the final composition. The alkaline metal is present as both metal and oxide and ranges from 0.9% wt. to 1.1% wt with respect to the final composition. The third component ranges from 0.01% wt. to 10% wt with respect to the final composition. Sn is present as both metal and oxide.
EP 1492620 discloses:                a catalytic composition containing a first component selected from noble metals (Pt) or mixtures thereof, a second component ranging from 0.9% wt. to 1.1% wt with respect to the total weight of the final composition selected from alkaline or alkaline earth metals, a third component selected from Sn, Ge, Pb, In, Ga, Tl and mixtures thereof, supported on alumina having a surface area ranging from 50 to 120 m2/g combined with a bulk apparent density higher than 0.5 g/cm3, wherein the molar ratio of the first component on the third component ranges from 1.5 to 1.7;        a catalytic composition comprising Pt, K in a quantity ranging from 0.9% wt. to 1.1% wt with respect to the total weight of the composition, a third component selected from Sn, Ge, Pb, In, Ga, Tl and mixtures thereof, supported on alumina (theta-alumina) having a surface area ranging from 50 to 120 m2/g combined with a bulk apparent density higher than 0.6 g/cm3, wherein the molar ratio of the Pt on the third component ranges from 1.5 to 1.7;        a process comprising a dehydrogenation step in a fluid or mobile bed wherein the hydrocarbon, preferably paraffins or C2-C30 olefins, is put in contact with the above catalyst, said step generating a stream rich in hydrogen in vapour phase, a separation step which generates a stream rich in liquid hydrocarbons which is further separated according to a fractionation scheme. The non-reacted hydrocarbons can be recirculated to the dehydrogenation step.        
According to EP 1492620, the carrier of the catalyst is alumina and it is essential for it to have a surface area ranging from 50 to 120 m2/g combined with a bulk apparent density higher than 0.5 g/cm3. The quantity of noble metal ranges from 0.01% wt. to 5% wt with respect to the final composition (0.01% wt. is equivalent to 100 ppm by weight). The alkaline metal is present as both metal and oxide and varies from 0.9% wt. to 1.1% wt. with respect to the final composition. The third component ranges from 0.01% wt. to 10% wt with respect to the final composition. The Sn is present as both metal and oxide.
KR 0142305 describes a catalytic composition for the dehydrogenation of paraffins which comprises from 0.1% wt. to 1.5% wt. of Pt, from 0.05% wt. to 1% wt. of tin, from 0.05% wt. to 1% wt. of Ga and from 0.5% wt to 5% wt. of an alkaline metal on gamma-alumina.
U.S. Pat. No. 4,914,075 discloses:                a catalytic composition containing a first component selected from noble metals (Pt), a second component selected from alkaline or alkaline earth metals present as both metal and oxide, a third component selected from Sn as both metal and oxide, Ge, Pb, In, Ga, Tl and mixtures thereof, supported on alumina having a surface area lower than 120 m2/g combined with a bulk apparent density higher than 0.5 g/cm3;        a process comprising a catalytic dehydrogenation step in a fluid or mobile bed starting from hydrocarbons such as paraffins and C2-C30 olefins, in particular butanes, which generates a stream rich in hydrogen in vapour phase, a separation step of the stream rich in hydrogen which generates a stream rich in liquid hydrocarbons which is further separated according to a fractionation scheme.        
According to U.S. Pat. No. 4,914,075, the carrier of the catalyst is alumina and it is essential for it to have a surface area lower than 120 m2/g combined with a bulk apparent density higher than 0.5 g/cm3. The quantity of noble metal ranges from 0.01% wt. to 5% wt with respect to the final composition. The alkaline metal is present as both metal and oxide and varies from 0.01% wt. to 10% wt. with respect to the final composition. The third component ranges from 0.01% wt. to 10% wt with respect to the final composition. The Sn is present as both metal and oxide.
U.S. Pat. No. 7,235,706 discloses:                a catalytic system containing gallium or gallium compounds (Ga2O3) in a quantity ranging from 0.1 to 33.6% wt., platinum in a quantity ranging from 1 to 99 ppm, oxides of alkaline or alkaline earth metals in a quantity ranging from 0% wt. to 5% wt. on alumina modified with silica, the silica being present in a quantity ranging from 0.08% wt. to 3% wt.;        a process for converting C2-C5 paraffins to C2-C5 olefins comprising a dehydrogenation step and a regeneration step of the catalyst.        
WO 2010107591 discloses:                a catalytic composition comprising a first component selected from Sn, Ga, Ge, Pb, In, Tl and their compounds among which the oxides (they are all alternative to each other), a second component selected from noble metals, from 0 to 2% wt. of an alkaline or earth alkaline metal also in oxide form, a carrier based on alumina or alumina modified with silica;        a catalytic composition comprising 0.25-5% wt. of a first component selected from Sn, Ga, Ge, Pb, In, Tl and their compounds among which the oxides (preferably Ga), from 5 ppm to 0.05% wt. of a second component selected from noble metals, from 0 to 2% wt. of an alkaline or earth alkaline metal also in oxide form, a carrier based on alumina or alumina modified with silica;        a catalytic dehydrogenation process of butanes to butylene with a regeneration step of the catalyst; the reactor can be a fast-riser.        
U.S. Pat. No. 6,281,160 discloses:                a catalytic composition comprising at least one carrier, at least one metal selected from group VIII (Pt) of the periodic table, at least one element M selected from Ge, Sn, Pb, Re, Ga, In and Tl, and also a metal selected from alkaline or earth alkaline metals; the carrier is an oxide among which alumina, silica alone or in a mixture;        a dehydrogenation process starting from butanes to the corresponding olefins which uses the catalyst claimed.        
The quantity of noble metals ranges from 0.1% wt. to 10% wt. The quantity of M ranges from 0.01% wt. to 10% wt. and the quantity of alkaline or earth alkaline metals ranges from 0.1% wt. to 3% wt.
U.S. Pat. No. 6,187,985 discloses:                a catalytic composition comprising at least one carrier, at least one metal selected from group VIII (Pt) of the periodic table, at least one element M selected from Ge, Sn, Pb, Re, Ga, In and Tl, and also a metal selected from alkaline or earth alkaline metals; the carrier is an oxide among which alumina, silica alone or in a mixture;        use of the catalyst in dehydrogenation processes of C5 paraffins which are recovered after extracting unsaturated compounds from the C5 fractions coming from steam-cracking or catalytic cracking.        
The quantity of noble metals ranges from 0.1% wt. to 10% wt, the quantity of M ranges from 0.01% wt. to 10% wt. and finally, the quantity of alkaline or earth alkaline metals ranges from 0.1% wt. to 3% wt.
A further critical aspect is linked to dehydrogenation catalysts containing significant quantities of platinum to be treated with chlorinated compounds or chloro-gas, or in regeneration phase or after this, to favour re-dispersion of the platinum to restore its catalytic activity. The treatment with chlorinated compounds is followed by reduction treatment in which the catalyst comes into contact with hydrogen to reduce the platinum to the metallic state before the dehydrogenation reaction. The use of chlorinated compounds leads to the introduction into the atmosphere of acid gases in addition to being critical for the corrosion of the equipment.